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<br />. <br /> <br />~.... <br />~ <br />'"" <br />"'-l <br /> <br />. <br /> <br />. <br /> <br />SPECIAL STUDIES (continued) <br /> <br />2 . <br /> <br />Salt From Surface Runoff <br /> <br />A number of activities, including livestock grazlng, off-road vehicle <br />use (ORV), oil and gas activity, mining claim exploration and development, <br />and coal mining activity, can be contributing factors to salt in surface <br />runoff from public lands. Each of these factors must be dealt with on <br />a site-specific basis to determine the extent of salt contribution and <br />to plan measures necessary to reduce the concentration to acceptable <br />levels. <br /> <br />Improper livestock grazing can have a significant influence on the <br />amount of sediment and salt yielded in surface runoff from rangelands. The <br />importance of controlling the period and intensity of grazing, the kind of <br />animal, and the need for rest from grazing to improve range condition is <br />stressed. Light to moderate grazing during the season when plants or soils <br />are least likely to be damaged, periodic rest from grazing through the use <br />of grazing management systems, and total removal of livestock from areas <br />with unstable soils or little potential to support a protective cover of <br />vegetation are specific ways livestock can be managed to reduce salinity. <br /> <br />Salinity control through grazing management will vary with <br />centration of salts in the soil. Specific management which may be <br />for each type is as follows: <br /> <br />the con- <br />employed <br /> <br />a. Nonsaline - Slightly Saline Lands <br /> <br />Grazing management to meet salinity objectives should strive to <br />produce a maxirnum volume of runoff while at the same time mai....~aining a <br />stable soil with a minimum loss of sediment through erosion. This loss of <br />water to the soil-water reservoir will reduce forage production for live- <br />stock and wildlife below its natural potential. However, the higher <br />quality water (usually below 300 mg/L salt concentration) will dilute the <br />more saline waters in the Colorado River system and at Imperial Dam, <br />and thus reduce salinity. <br /> <br />b. Moderately Saline Lands <br /> <br />Grazing of livestock at a light to moderate level, in accordance with <br />a schedule of use and rest treatments designed to provide maximum protec- <br />tion for soil and plants, will reduce salinity in surface runoff. The <br />objective on these lands is to increase infiltration and reduce runoff and <br />loss of saline sediment. Salt concentration in runoff water exceeds that <br />measured in receiving streams. <br /> <br />c. Highly Saline Lands <br /> <br />Moderate grazing in winter when soils are frozen may not significantly <br />increase salinity on areas where forage production is sufficient to support <br />grazing animals. Soil factors have a most important influence on infiltra- <br />tion and runoff on areas having a very sparse ground COver of perennial <br />vegetation. Plants have only a slight influence due to their scarcity. <br /> <br />120 <br />